My first thoughts were along what bigbulls posted as well though even if it were a 260 grain 320 fps arrow I would still choose the heavier one.

I'd glue the 260 grain arrow inside the 400 grainer. That way, I'd wind up with an arrow that weighs a decent amount.

Sorry I meant 360 grains. Does it still mean the same answer?

remember, the name of the game is kinetic energy. to accomplish this, shoot the heavier arrow faster, thus increasing energy, and reducing shock on the bow

Actually, the name of the game is momentum. The good news is that the heavier arrow wins in both categories.

Taking into consideration that 20 fps won't do a whole heckuva lot to help your trajectory within average hunting shot distances, then it becomes a no-brainer.

U R correct, momentum is the name of the game. Is momentum and kinetic energy synonymous? Meaning, that a heavier arrow will retain speed downrange, which also means it will have more kinetic energy downrange

Actually the name of the game is puting the arrow in the right spot . Light or heavy you gotta get it there first.

40 grains difference in arrow weight isn't gonna make a hill of beans difference in penetration on white tail deer.

Shoot the arrow that your bow likes. It's a lot like bullets and guns. Some are tack drivers, some are acceptable and some are down right sporatic. Your bow will tell you what it likes.

I'd go with the heavy arrow..........that's about what I'm shooting now.

aha i knew science class would pay off o wait im still in that class and thats what im studian u want the most moementum mass times velosity the great the more punch its gonna have when that big bruiser steps out of the brush[:-]

True enough, bigbulls. I was operating on the assumption that the arrows were already determined to be equal in accuracy.

As to whether 40 grains would make a hill of beans difference on penetration... You don't know that any more than I know otherwise. On a standing, broadside shot where the deer lets you shoot him and doesn't move a muscle, yes you're probably right. On a shot where the deer decides to spin, duck and tear out, then who knows when even an extra half inch of penetration might make the difference between a short blood trail and a wounded/lost animal.

Too many people are rigging up their hunting gear purposely for ideal situations. Shooting the lightest arrows they can get away with is WAY up towards the top of the list on stuff that can work when everything goes right, but it's also way up the list of stuff that can turn on you and bite your buns when the least little thing goes wrong... You gotta consider that those ideal situations can turn into nightmares in a splintered instant.

You know, I quit watching bowhunting videos several years ago because I got absolutely sick of watching carbon arrows come to a screeching halt after about 6" of penetration in the rib cages of the deer they were shooting. The editors would always do a quick cut just after the impact and go to the hero shot, but playing the tapes in slo-mo would prove the arrows stopped dead. Back when everyone was shooting substantially heavier aluminum arrows on the videos, you rarely saw a shot that didn't whistle right thru.

I'm glad to see people starting to allow for a little margin of error in the stuff they take to the woods by choosing heavier arrows for hunting. I know they are doing so because several carbon arrow manufacturers are offering heavier arrows now. They wouldn't be doing that if the demand wasn't there.